Wastewater treatment process may keep fish off antidepressants

While some people may wonder about the possible side-effects of antidepressants on the people who are taking them, here’s another thing to consider ... what happens when the residue from those drugs passes through the user’s urine and into the sewage system? As it turns out, it can enter local waterways and affect the fish. Now, researchers from KTH Royal Institute of Technology in Stockholm have developed technology to keep that from happening.

In a study recently conducted at Sweden’s Umeå University, perch were exposed to the anxiety-moderating drug Oxazepam, in concentrations similar to those found downstream from sewage treatment plants. It was observed that the normally-shy fish became bolder, venturing away from their protective schools to hunt for food – a behavior that makes them more likely to be eaten by predators.

It was additionally noted that they ate more quickly. This could allow them to eat a greater amount overall, potentially throwing ecosystems out of balance, and creating algae blooms via increased amounts of feces.

Umeå environmental chemist Jerker Fick was quoted as saying, “The solution to the problem is not to stop medicating ill people, but to try to develop sewage treatment plants that can capture environmentally hazardous drugs.” Apparently, that’s what KTH has done.

The technology utilizes a process known as membrane distillation, in which liquid water passes through a microporous membrane in the form of water vapor – once on the other side of that membrane, the vapor moves across an air gap and then condenses on a collecting plate, thus returning to its liquid state. Antidepressants in the unfiltered liquid are unable to pass through the membrane, so they end up collecting on its liquid, “dirty” side.

The water temperature reportedly doesn’t need to be particularly high in order for the process to work.

The membrane distillation demo project at Hammarby Sjöstadsverket

A large-scale membrane distillation system has been set up at KTH’s Hammarby Sjöstadsverket water treatment test facility. When wastewater containing 282 nanograms of Oxazepam per liter was treated, the concentration dropped to under two nanograms per liter – in an ordinary treatment plant, virtually none of the Oxazepam would have been removed.

The results have been similar with most other medications tested. “Of all the 20th century-tested drugs, it is only the remains of the antidepressant Sertraline that we failed to clear 100 percent,” said KTH’s Prof. Andrew Martin. “We have some theories, but cannot yet explain why.”

An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.